The present application relates generally to power supplies, and more specifically to power selection circuitry that may be employed in redundant power supplies.
Redundant power supplies are known that are capable of providing multiple input voltage sources to a load to assure that power continues to be provided even when one of the input voltage sources fails. For example, a conventional redundant power supply may comprise first and second input voltage sources, and power selection circuitry including first and second switching elements selectively connecting the first and second voltage sources, respectively, to a load. In a typical mode of operation, when the first voltage source is operational and the second voltage source is not fully operational, the first switching element is activated to connect the first voltage source to the load and the second switching element is deactivated to disconnect the second voltage source. Similarly, when the second voltage source is operational and the first voltage source is not fully operational, the second switching element is activated to connect the second voltage source to the load and the first switching element is deactivated to disconnect the first voltage source.
One drawback of the above-described conventional redundant power supply is that the power selection circuitry employed therein may allow cross-conduction of current to occur between the multiple input voltage sources. For example, when the first switching element is activated to connect the first voltage source to the load and the second switching element is ostensibly deactivated, the second switching element may allow at least some current to flow back to the second voltage source, thereby causing the second voltage source to become a sink and possibly leading to an overload of the second voltage source. Similarly, when the second switching element is activated to connect the second voltage source to the load and the first switching element is ostensibly deactivated, the first switching element may allow at least some current to flow back to the first voltage source, possibly causing an overload condition at the first voltage source. Moreover, the conventional redundant power supply has other drawbacks, e.g., the power selection circuitry is often susceptible to load current spikes when the switching elements are activated to connect selected ones of the multiple voltage sources to the load.
It would therefore be desirable to have power selection circuitry usable in redundant power supplies that avoids the drawbacks of the above-described conventional circuitry.